When I move the bellows open to fill it with air, my pipes give off a rather flatulent belching sound--kind of a soft grunting noise. The sound is coming from where the hose enters the bag. After taking it apart, it's apparent that the little leather flap that covers the airway is rapidly and repeatedly opening and closing, which causes the noise. It seems to do the job of sealing the hose when I"m squeezing the bag to play the chanter (no burping). And when I squeeze the bellows to fill the bag, it stays open while the air flows from the bellows to the bag...so no burping then either. It's only when I'm moving the bellows to the out position that it creates just enough suction to cause it to flap, but not enough to keep it sealed. It only happens at the initial opening movement of the bellows.

Not a huge deal...but not very appealing when you are preparing to play a tune and it creates a funny grunting noise.

Make sure that the flap is positioned so that it is hanging completely downward according to the way you hold the bag while playing. It stays in position mainly by gravity so you want it to be hanging vertically for a good seal.

If this is an older set the leather flap may be a bit dried out. A TINY amount of leather softener may be helpful in returning the flap to being soft and supple enough to maintain a good tight seal.

Also check for any debris - dust or fluff - that might be preventing the valve from closing down completely. The contact point for the valve needs to be completely flat, so also check that no rough edges have been left that might also be preventing a good efficient seal.

Additionally, the flap itself may be a little on the light side. Also check for airtightness in the wrappings on your bellows connector and, while you're at it, check the flap valve in both bag and bellows.